Electromagnetic device



Nov. 2, 1937. w. c. ROE 2,097,323

ELECTROMAGNETIC DEVICE Filed April 28, 1934 INVENTOR.

,J; ATTORNEY$ Patented Nov. 2, 1937 UNITED STATES nu:c'raormeur.'rro nnvrcn William C. Hoe, Elyrla, Ohio, asaignor to Robert B. Brewer, Cleveland, Ohio Application April 28, 1934, Serial No. 722,938

3 Claims.

My invention relates to electro-magnetically operated mechanisms and relates more particularly to striker mechanisms for use with chimes or other musical instruments.

It is an object of this invention to produce a maximum power stroke from a limited amount of applied electrical ene Another object of the invention is to construct a striker mechanism or the like for musical instruments employing a'vibratable element, wherein the rebound speed of the striker is greater than the rate of vibration of the vibratable element when the latter is struck.

My invention has for another one of its ob- 5 jects to eliminate extraneous noise and vibration of an armature actuated electro-magnetically, and to further eliminate substantially all alternating hum or chatter.

-A still further object of the invention is to 20 produce an electro-magnetically operated striker mechanism having the above desired characteristics, and which is extremely simple in construction and design and which is further equally well adapted for use with both alternating and direct 25 current.

Other objects and advantages of my invention will become more apparent as the following description of two embodiments thereof progresses, reference being made to the accompany- 30 ing drawing in which like reference characters are employed to designate like parts throughout the same.

In the drawing: I

Figure 1 is a vertical section of a musical in- 5 strument such as a chime, showing one form of my invention applied in use, the electro-magnetically operated striker mechanism being shown in side elevation and housed within a resonance chamber;

40 Figure 2 is a side elevation of the same embodiment of my invention shown in Figure 1 and shows the relative positions of the armature and magnet cores when the magnets are deenergized; I

45 Figure 3 is a similar view of the same embodiment of the invention showing the relative positions of the armature and magnet cores at the beginning of the power stroke, as when the magnets are energized;

Figure 4 is still another view of the same embodiment illustrating the position of the armature at the peak of the power stroke;

Figures 5, 6 and 7 illustrate a second embodi- 55 ment of my invention and correspond respectiveiy to Figures 2, 3 and 4 illustrating the first embodiment; and

Figure 8 is a front elevation of the device shown in Figure 2.

It is to be understood that while I have shown 5 but two embodiments of my invention in the drawing and have shown the same applied in use in connection with a musical instrument, such as a chime, that the invention is not to be considered to be limited to such use or to the 10 specific structure shown in the drawing, since other adaptations of the invention coming within the scope of appended claims and the purpose of the invention readily may be made.

Referring now more particularly to Figures 1, 2, 3, 4 and 8 I will proceed to describe the particular embodiment illustrated therein.

In Figure 1 I have shown this embodiment applied in use in connection with a musical chime in which I represents an elongated tubular resonance chamber. The resonance chamber l is provided with a restricted opening 2 intermediate its ends in one face thereof, through which the striker 3 is projected to momentarily strike the vibratable element 4. It is to be noted that in the present embodiment the striking mechanism is mounted as a unit entirely within the resonance chamber i, and that the vibratable element or reed 4 is mounted on the outside of the resonance chamber and in spaced relation thereto by means of the brackets 5, the'reed l overlying the restricted opening 2 and located in the path of movement of the strikert. 'I'he reed l is suspended from the brackets 5 by any suitable meanssuch as the springs 6, which may be similar to the type of spring shown in my copending application, Ser. No. 674,338, filed June 5, 1933. The present invention, however, relates more particularly to the striker mechanism which is designed as a unit to be mounted 40 within the resonance chamber i.

In carrying out the invention as illustrated in the drawing the coils l are mounted side by side on a plate 8 by means of the bolt or screw l0. A layer of fiber or other insulating material II is interposed between the plate 8 and the plate 21 and each of these elements is firmly clamped or secured together when the bolt ill is tightened to rigidly support the coils I and bracket l2 thereon. The armature supporting bracket I2 is substantially L-shaped in cross section, the base comprising a pair of forwardly extending supports I 3, one extending forwardly below each of the magnet coils and spaced from each other to provide ample space between them for the spring I and for the depending portion of the armature IS. The forward ends of the bracket members l3 are bent upwardly as at IE to provide forward stops on opposite sides of the armature body l'l (see Figure 4) during the approach of the armature to one of its extreme limits of motion. It will be noted that the bracket members l3 are inclined first slightly upwardly as at l8 before terminating in the pending arm I 5 to which is detachably secured at its lower end, the striker member 3. It is pre-.

ferred that the striker element 3 be weighted sufficiently to give an efiective stroke when the armature is actuated in response to the energization of the magnets I. The striker 3 is provided with a soft tip 20 of leather or other suitable material .which is commonly used in such devices and is adapted to sharply engage the vibratable element 4 to deliver a sharp blow thereto. The armature l5 carries a cross member 2i which is secured to its rear face by means of a screw 22. The member 2| is formed with oppositely disposed arms 23 which operate just below the under surface of the bracket members l3 and serve as stops for the armature during its retraction or toward the backwardlimit of its motion as indicated in Figure 1. The member 2| terminates at its lower end in a hook 24 to which one end of the retraction spring I4 is attached, the opposite end of the spring I being attached to the bracket l2 as at 25. It is sufficient that the spring retract the weighted armature to a position such as indicated in Figure 1 and to retain the same in that position while the magnets I are de-energized.

The coils I may be connected in series electrically and their free ends are connected to a pair of insulated binding posts 26 projecting from the rear of the mounting plate 21.

The resonance chamber l is provided with an opening in one of its walls for receiving the striker unit for mounting within the chamber. In the embodiment illustrated this opening is indicated at 2B in the rear wall of the chamber l and at the upper end thereof. It is to be understood, however, that this opening may be otherwise located in the chamber to suit various conditions if desired.

The lower end of the plate 21 is upset as at 23 to form a socket 30 with the rear wall of the chamber which it overlies when the unit is assembled within the chamber. Suitable screws 3| are provided to removably secure the plate 21 to the chamber.

The resonance chamber I may be suitably tuned to proper resonance with the period of the vibratable element 4 by means of the partition 32. This partition may be of soft material and is cut to fit the internal cross section of the chamber. chamber and may be fixed therein in proper adjustment by any suitable means. A similar member 33 may be inserted against the top wall of the chamber. By such construction internal chatter or noise is substantially eliminated.

It is adjustable vertically within the The operation of this embodiment of my invention may be described as follows:

The unit shown in Figure 8 is inserted through the opening 28 in the chamber I with the plates 9 and 21 closing the opening. This is clearly shown in Figure l. The screws 3| are driven home to securely, but removably, fasten the unit in place. A source of electrical energy with a suitable switch (not shown) may be connected to the binding posts 26 and when the circuit is closed the coils I will be energized.

Figures 2, 3 and 4 represent the three principal phases of the operation of the striker in delivering a sharp impact blow to the vibratable element 4. In Figure 2 the armature and striker are fully retracted by means of the spring I4. In this position the armature i'i engages the pole pieces l9 only in point contact along their lowermost edges. Energization of the coils 1 sets up a magnetic field at the poles which is sufilcient to quickly draw the armature head I! toward the pole pieces against the tension of the spring I. It is to be noted that the armature rocks about the point contact at 34 to assume a position as in Figure 3, that is where the armature lies fiat against the pole pieces. The next position of the armature results from a further rocking of the same until it again is in point contact with the upper edges of the pole pieces as at 35 in Figure 4. This power stroke of the armature, the depending arm l5 and the striker 3 is accomplished while some portion of the armature is always in contact with the pole pieces, thereby reducing and substantially eliminating chatter and noise or hum. This is particularly noticeable when the device is operated by A. C. current. Furthermore by thus eliminating the air gap between the armature and the pole pieces at the start and during the stroke, the striking powerof the striker 3 is materially increased. The contact of the armature with the cores between points 34 and 35 eliminates the air gap and tends to first decrease and thus increase the magnetic leakage. The armature rocks on the cores and tends to draw to the point of greatest density of magnetic flux. The inertia of the striker 3 carries the armature slightly beyond this point until it strikes the vibratable member 4, and against a portion of the magnetic pull of the cores which affects the armature in a reversed direction as a rebound pull. This is illustrated in Figure 4 where the armature contacts only with the upper edge of the cores l9 as at 35. This is at the end of the power stroke and the magnetic pull of the cores will tend to pull the armature back toward the normal position, constituting a rebound action.

As a result the striker is quickly retracted and such action is further assisted by the retracting spring II. In the rebound movement of the striker the magnetic pull, the spring I 4 and the resiliency of the striker tip all contribute to a quick return of the striker at a speed which is faster than the retm'n movement of the element 4 after it is struck.

The armature rests and slides upon the brackets l3 and is otherwise possessed of a freedom of movement within the limits defined by the coils or the stop 2i and the portion I6. Lateral freedom is also provided as indicated in Figure 8, but very little lateral movement will be required.

In Figures 5, 6 and 7 I have illustrated a modi-. fication of my invention which is quite similar to the form illustrated in Figures 1 to 4 inclusive, except for the armature. In the present embodiment the armature III is arcuate or curved in cross section or end elevation as indicated. In this manner the armature striker member will be caused to roll upon the cores ll of the magnets when the latter are momentarily energized. As in the case of the first described embodiment, the armature 40 is at all times in contact with the pole faces or cores 4| The normal retracted position of this modified armature is shown in Figure 5 and at the beginning of the power stroke the armature is in but point contact as at 42 with the lower edge of the cores. When the magnets are energized the armature is caused to roll quicklyas in Figures 6 and 7 to thrust the striker 3 outwardly through the opening 2 in the resonance chamber and into sharp but momentary contact with the member 4.

When either embodiment is assembled as shown in Figure l, the device constitutes a very compact simple structure, possessing a pleasing tone and readily adapted for various uses. For

instance, the device may be used in-place of a door bell orothg call device, or it may be used as a ringer for telephoneswrtlle like. Because of its simplicity of construction a'nd easy manner of assembly, it is very economical to manufac-- ture. I have found that devices embodying my invention can be operated with extremely low power consumption and because of this feature the device is particularly useful as door alarms,

since it will operate efllciently on from 1 to 6 volts if desired.

Various changes in the details of construction and arrangement of parts may be made without departing from the spirit of my invention or th scope of the appended claims.

I claim:

1. A striker device for musical instruments and the like comprising a striker having a substantial mass at one end, a support pivotally supporting said striker adjacent the other end, an electromagnetic means arranged to attract the end of the striker remote from said mass and beyond said support to oscillate said striker, said electromagnetic means having a core face lying in a plane intersecting that portion of the striker near its pivoted end when the striker is at rest whereby said means will exert its maximum pull when the striker is in the lowermost position of its swing.

2. A striker device for musical instruments and the like comprising a striker having a substantial mass at one end, a support pivotally supporting said striker adjacent the other end, an electromagnetic means arranged to attract the end of the striker remote from said mass and beyond said support to oscillate said striker, said electromagnetic means having'a core face lying in a plane intersecting that portion of the striker near its pivoted end when the striker is at rest whereby said means will exert its maximum pull when the striker is in the lowermost position of its swing, and a fulcrum remote from said support about which said striker may oscillate after it. has reached said lowermost position.

3. A striker'device for musical instruments and the like including an electromagnet, an armature support associated therewith and extending below and beyond one end thereof, a striker suspended from the support and in slidable engagement therewith, said striker having an armature portion extending above the support and movable in the magnetic field of the electromagnet when the latter is energized, that portion of the striker which is suspended below the support being provided with a weighted mass.

WIILIAMIC. ROE. 

